1. Field of the Invention
The present invention relates to a connection arrangement between a frame member and an engine of a saddle-type vehicle, and to a vehicle incorporating the same. More particularly, the present invention relates to an engine-fastening structure of a saddle-type vehicle, and a vehicle incorporating the same.
2. Description of the Background Art
In a motorcycle, which is one example of a saddle-type vehicle, normally the engine is a component having the highest weight. It is known that fastening of the engine and a frame to each other is a significant factor in setting for vibrations and traveling behaviors, as discussed in the Japanese Patent Laid-Open No. 2005-014885.
For example, it is well known that vibrations or the rigidity of a finished vehicle varies depending upon whether rigid mounting or rubber mounting is used for an engine. In a motorcycle wherein an engine is mounted on a frame by rigid mounting, the engine and the frame are fastened to each other with a collar interposed therebetween. The collar can make relative displacement to the bolt by a very small distance in a diametrical direction because a clearance of approximately 0.3 mm exists between the collar and the fastening bolt.
The relative displacement between the collar and the bolt is suppressed by friction between a frame side seating face and an engine side seating face upon which axial force of fastening acts. In a motorcycle which adopts the rigid mounting, the contact state of the components mentioned is maintained with certainty to achieve stabilization of vehicle body vibration and the control performance.
If a motorcycle wherein an engine having high weight is rigidly mounted through a collar travels on a road having a large gap, then the vehicle undergoes upward and downward vibrations, and a load higher than holding force of the contact seating faces at the opposite ends of the collar may be generated at the fastening portions and the fastening bolt may undergo shearing deformation and may be plastically deformed by a very small amount.
If the fastening bolt is plastically deformed, then variation of the contacting portions of the frame, collar and engine and variation in contact pressure distribution of the seating faces occur. This sometimes results in failure in stabilized seating face contact and in variation of vibrations or the drivability.
In such an instance, the structure of the fastening portion between the frame and the engine is set appropriately in accordance with the vehicle. In the prior art document, a structure is disclosed wherein, in an engine supporting structure for a motorcycle where a collar is interposed between a frame and an engine, wedge-like projections are provided on opposite end seating faces of the collar.
With a structure such as described above, it is possible to effectively suppress the relative displacement between the collar and the bolt.
However, according to the conventional structure, the cost required for working of the collar is high. Further, positioning in a circumferential direction of the collar is required, and time and labor are required for assembling these components.
The present invention has been made in view of the situation described above. Accordingly, it is one of the objects of the present invention to provide a saddle-type vehicle having an engine-fastening structure which stabilizes seating face contact between a frame and a collar, and between an engine and the collar and is low in cost and easy in fastening working.